PTSD and chronic pain are highly prevalent and each is associated with long-term disability and substance abuse, exacting enormous emotional, functional, and financial tolls on individuals and society. PTSD and chronic pain are frequently co-morbid with overlap between 20% and 70%, representing an enormous public health problem. However, our understanding of the mechanisms by which PTSD and chronic pain become intertwined is limited. The majority of studies of the PTSD/chronic pain co-morbidity are cross- sectional, and focused on a single chronic pain condition, limiting causal inferences and generalizability to other chronic pain conditions. Chronic pain is also related to a high prevalence of substance abuse. To understand how trauma-related PTSD, and resilience and vulnerability factors contribute to the transition from acute to chronic pain and development of substance abuse requires prospective designs. Such research is vital among inner-city African American women, who are more likely to experience traumatic stress and pain, but are less likely to be treated appropriately; a phenomenon perhaps leading to greater risk for disability and substance abuse. We propose to examine 3 models related to the development of PTSD/chronic pain pairing and development of substance abuse in people initially presenting with acute pain (not caused by a traumatic event) in a 6-month prospective design. First is the Main Effects Model in which the level of PTSD symptoms at baseline will predict the likelihood of a transition from acute to chronic pain and development of substance abuse at 6 months. Second is the Moderation Model in which baseline vulnerability and resilience factors interact with PTSD symptoms to predict the likelihood of developing chronic pain and substance abuse 6 months later. Third is the Mediator Model in which relationships between baseline levels of PTSD symptoms and the development of chronic pain and substance abuse 6 months later are mediated by vulnerability and resilience factors at 3 months. Inner-city women (N=600) presenting to an Emergency Department with a complaint of acute bodily pain, ages 18-40 yrs, will be recruited. Only women presenting with acute pelvic/abdominal, neck/shoulder or low back pain, and who do not have a chronic pain history will be enrolled. We will assess trauma exposure, PTSD symptoms, pain sensitivity, substance dependence and abuse, acute pain and psychosocial resilience and vulnerability factors across 3 waves (baseline, 3- and 6-months), and obtain additional phone assessment of pain intensity and interference at 1-, 2-, 4-, and 5-months. Inner-city women were chosen because of their high likelihood of exposure to ongoing traumatic events and the opportunity to illuminate a health disparity involving the PTSD/chronic pain pairing among inner-city minority women in particular. The public health problem posed by co-morbid PTSD, chronic pain and substance abuse cannot be overstated, particularly as it impacts health disparities in the US. Greater understanding of how PTSD may increase the likelihood of transitioning from acute to chronic pain and developing substance abuse, which factors contribute to these developments, and which people may be most vulnerable will allow more timely clinical interventions on accurately identified targets to help forestall the development of these largely intractable conditions.